In total hip replacement surgery, a patient's natural hip is replaced by an acetabular cup component that replaces the acetabular socket and a femoral component that replaces the femoral head.
The femoral component of the hip prosthesis includes a generally spherical head, connected via a neck portion, to an elongate stem. The patient's femur is prepared to receive the stem. The proximal end of the femur is resected to expose the medullary canal. This involves resection of at least part of the greater femoral trochanter, and the creation of a cavity that matches the shape of the implant stem.
Surgeons may use several different instruments such as an osteotome, rasp, canal probe, and starter broach to initiate the canal. Changing between instruments takes time. Additionally, the number of instruments required for surgery indirectly increases cost of a procedure.
There is therefore a need for a multifunctional instrument that combines the functionality of existing instruments.
To help ensure proper final orientation of the stem, lateral bias during implant preparation may be preferred. Retraction of the gluteus medius and removal of the lateral cortical bone at the trochanteric fossa helps the surgeon to obtain optimal proximal fit of the stem. This also reduces the risk of undersizing and/or varus placement of the stem.
Surgeons currently face several challenges when using traditional osteotomes. For example, the surgeon conventionally positions the osteotome relative to external anatomical landmarks, such as the trochanteric fossa, in an effort to position the osteotome to cut the desired bone leading to the femoral canal. Since every bone is shaped differently, the surgeon may not correctly predict the starting position which would lead to the desired bone removal. This may be further exacerbated by a poor grip between the osteotome and the bone surface, resulting in slippage of the osteotome after initial placement caused by impaction strikes.
The surgeon also conventionally angles the osteotome relative to the external anatomical landmarks, such as the femoral leg axis, in an effort to direct the angle that the osteotome resects the bone. Since it is often difficult to visualize the external anatomical landmarks and to hold the osteotome at the desired angle while impacting, the surgeon may not achieve the desired angle of bone removal.
The necessary amount of lateral bone may not be fully removed by the first cut. This is particularly true if the surgeon adopts a conservative and iterative bone cutting approach. Thus, further cuts with the osteotome, or removal of the bone with other instruments (e.g., rasp, rotational initiator or broach) may be required.
There is therefore a need for an improved osteotome that does not rely on external visual landmarks for positioning. There is also a need for an osteotome having an improved grip on the proximal surface of the femur.